Air circuit breakers as described within U.S. Pat. Nos. 3,095,489 entitled "Manual Charging Means for Stored Energy Closing Mechanisms of Electric Circuit Breakers" and 3,084,238 entitled "Ratchet Mechanism for Charging a Closing Spring in an Electric Circuit Breaker" include operating mechanisms that are mainly exposed to the environment. Since the air circuit breakers are rated to carry several thousand amperes of current continuously, the exposure to convection cooling air assists in keeping the operating components within reasonable temperature limits.
Such air circuit breakers are usually provided with a motor operator such as described in U.S. Pat. No. 4,167,988 entitled "Ratcheting Mechanism for Circuit Breaker Motor Operator" or a manual handle as described in U.S. Pat. No. 3,729,065 entitled "Means for Charging A Stored Energy Circuit Breaker Closing Device" for charging the powerful closing springs contained within the air circuit breaker operating mechanism.
As described within the aforementioned U.S. Pat. No. 4,167,988, the ratchet mechanism includes a driving pawl coupled with the motor operator for incrementally advancing a ratchet wheel coupled with the circuit breaker operating mechanism. Each incremental advance of the ratchet wheel is sustained by a holding pawl. Ultimately, the ratchet wheel is advanced to an angular position where the circuit breaker closing springs are fully charged and therefore empowered to forcibly close the circuit breaker contacts. Typically, the discharge of the closing springs rapidly drives the ratchet wheel in the same direction as did the driving pawl in charging the closing springs. In the process, the teeth on the ratchet wheel impact with the driving and holding pawls, producing undue pawl and ratchet wear, as well as unnecessary stress on the pawl springs and mountings. Moreover, when the breaker contacts close, there is an inevitable rebound which tends to rotate the holding pawl. Under these circumstances, the straight sides of the ratchet teeth impact against the straight edges of the pawl tips, causing potentially damaging stresses in the ratcheting mechanism. The patent further suggests the use of a holding prop to hold the pawls out of engagement with the ratchet wheel until the closing springs have fully discharged to protect the pawls and the ratchet wheel from potential damage. When the contacts have become closed, the circuit breaker operating mechanism components are exposed to allow an operator to manually release the holding prop in order for the holding pawl to again become operative in recharging the circuit breaker closing spring.
When the circuit breaker closing springs are brought to their fully-charged conditions, it is important that the springs do not become inadvertently discharged while an operator has hold of the charging handle in order to avoid damage to the ratchet mechanism and the associated air circuit breaker contacts. An early arrangement of a latching means to prevent rotation of a closing springs charging handle is found in U.S. Pat. No. 4,475,021 entitled "Air Circuit Breaker".
When the circuit breaker closing springs are completely charged, the holding pawl is removed from the charging gear to allow the charging shaft to rotate when the circuit breaker closing button is activated, as described in U.S. patent application Ser. No. 08/863,649 entitled "Ratcheting Mechanism for an Industrial-Rated Circuit Breaker", filed 27 May 1997. With the holding pawl removed from the charging gear, the closing springs exert a force of rotation on the charging shaft and some means must be employed to assure that the charging shaft remains in a closing springs "charged condition" until and unless the circuit breaker closing button is activated, as described in U.S. patent application Ser. No. 08/865,165 entitled "Closing Springs Release Mechanism for Industrial-Rated Circuit Breaker", filed 28 May 1997.
When the circuit breaker closing springs are fully-charged, they are ordinarily released by means of a closing button arranged on the circuit breaker cover next to the circuit breaker operating handle. Should an operator attempt to depress the closing button while lifting the operating handle, the force exerted on the handle by means of the released closing springs could cause damage to the circuit breaker internal operating components.
One purpose of the invention is to interlock the circuit breaker operating handle with the circuit breaker closing button to prevent the circuit breaker closing springs from becoming closed unless the operating handle is completely in the home position.